参数资料
型号: MAX5026EVKIT
厂商: Maxim Integrated Products
文件页数: 9/13页
文件大小: 0K
描述: EVAL KIT FOR MAX5026
产品培训模块: Lead (SnPb) Finish for COTS
Obsolescence Mitigation Program
标准包装: 1
主要目的: DC/DC,步升
输出及类型: 1,非隔离
输出电压: 30V
电流 - 输出: 6mA
输入电压: 3 ~ 11V
稳压器拓扑结构: 升压
频率 - 开关: 500kHz
板类型: 完全填充
已供物品:
已用 IC / 零件: MAX5026
500kHz, 36V Output, SOT23,
Step-Up DC-DC Converters
Determining the Inductor Value
ULVO
OSCILLATOR
THERMAL
SHUTDOWN
47μH is the recommended inductor value when the out-
put voltage is 30V and the input voltage is 5V. In gener-
al, the inductor should have a current rating greater
than the current-limit value. For example, the inductor’s
current rating should be greater than 150mA to support
3
FB
REF
-A
+A
MAIN PWM
COMPARATOR
CONTROL
LOGIC
SHDN
LX
4
6
a 4mA output current. Equivalent series resistance
(ESR) should be below 1 Ω for reasonable efficiency.
Due to the MAX5025–MAX5028’s high switching fre-
quency, inductors with a ferrite core or equivalent are
recommended. Powdered iron cores are not recom-
2
GND
+C
-C
CURRENT-
mended due to their high losses at frequencies over
500kHz. Table 1 shows a list of vendors and 47μH
LIMIT
COMPARATOR
inductor parts.
For 4mA output current and output voltages other than
5
V CC
N
PGND
1
30V, the inductor can be simply scaled in value
according to the following formula:
MAX5025
L =
( 47 μ H ) ( V OUT ? V IN )
( 25 V )
Figure 1. Functional Diagram
MAX5026
Use the following formula to calculate the upper bound
of the inductor value at different output voltages and
output currents. This is the maximum inductance value
for discontinuous mode operation.
R 1 = R 2 ? OUT - 1 ?
? V ?
? V REF ?
L UPPER =
2
V IN ( V OUT ? V IN ) T S η
2
2 I OUT V OUT
2 T S ( V OUT ? V IN ) I OUT
I LPEAK =
2 T S ( V OUT ? V IN ) I OUT
L LOWER =
? V
?
η ? IN ( ) ?
? 5
?
where V REF is 1.25V
Determining Peak Inductor Current
If the boost converter remains in the discontinuous
mode of operation, then the approximate peak inductor
current, I LPEAK , is represented by the formula below:
η L
where T S is the period, V OUT is the output voltage, V IN
is the input voltage, I OUT is the output current, and η is
the efficiency of the boost converter.
Table 1. Inductor Vendors
Calculate the lower bound, L LOWER , for the acceptable
inductance value using the following formula, which will
allow the maximum output current to be delivered with-
out reaching the peak current limit:
2
260 mA
Notice that the switch current limit, (V IN /5)(260mA), is a
function of the input voltage, V IN . The current rating of
the inductor should be greater than the switch current
limit.
VENDOR
Coilcraft
Sumida
Toko
PHONE
847-639-6400
847-545-6700
847-297-0070
FAX
847-639-1469
847-545-6720
847-699-7864
PART NUMBER OF 47μH INDUCTOR
DT1608C-473
CDRH4D28-470
A915BY-470M
_______________________________________________________________________________________
9
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